The invention pertains generally to cleaning methods and especially to methods for removing residues produced in refrigeration systems.
Refrigeration systems operate by alternately compressing and vaporizing a refrigerant, such as trichlorofluoromethane (CFCl.sub.3). Usually, a small amount of compressor oil is admixed with the refrigerant. Also to be found with the circulating refrigerant are small amounts of water, air, metal (e.g., iron, aluminum, and copper), and oxides and salts of those metals. During the operation of the refrigeration systems, these materials slowly react and accumulate on the surfaces, such as, walls and impeller blades of the refrigeration system. This residue resembles varnish or coke. It is these polymers and halogenated polymers with metals, salts, and oxides admixed therein that render cleaning refrigeration systems nearly impossible.
Presently, several chemical techniques are used, e.g., solutions of citric acid, salts of ethylenediaminetetraacetic acid, modified solutions of hydrochloric acid or phosphoric acid. The major disadvantages associated with the use of these cleaning solutions are poor cleaning and surface corrosion.